Across the stubbled plains of Namibia and southern Angola, barren terracotta-colored circles known as fairy rings spot the desert landscape like confetti. The sight is simultaneously weird and wonderful, all the more so because after 30 years of research scientists continue to scratch their heads in bewilderment, unable to explain the cause or purpose of the rings.

Several theories have been advanced over the years to unravel the mystery of the circles, which range in diameter from 6.5 feet to nearly 40 feet (2 to 12 meters) and are edged by densely growing grass. One theory held that radiation inhibited plant growth, while another suggested previous flora had poisoned the earth. Both were dispelled in 2000, when a group of scientists working under laboratory conditions grew plants in soil taken from the barren patches.

Another theory, proposed in 2001 by C. F. Albrecht from Stellenbosch, South Africa, suggests that termites living deep underground release a chemical that kills the grasses above. But why would termites kill off large patches of potential food? For another important element: water. Rainfall pools in the depression of each circle, then stays in the soil rather than being depleted by plants. Albrecht and his team found that after heavy rainfall, soil inside the fairy rings contains five times the water content of soil outside.

Even Albrecht's theory is being contested. While he claims the barren patches are dynamic, meaning they go bald, grow over again, and move around, others insist they are stationary, undergoing little change from decade to decade. A study published in 2004 by M. W. van Rooyen from the University of Pretoria in South Africa examined all previously conducted surveys and discounted each one, including Albrecht's. Rooyen's team also stated that their own soil-moisture measurements were inconclusive.